1. Field of the Invention
The present invention generally relates to a solder printing apparatus for inspection of solder printed on a printed circuit board and also relates to a solder printer system equipped with the solder printing apparatus.
2. Background Art
In order to mount electronic components on a printed circuit board, generally cream solder is first printed by a solder printer on multiple lands formed on the printed circuit board. Next, the electronic components are provisionally set on the printed circuit board using the viscosity of this cream solder. Thereafter, the above-described printed circuit board is loaded into a reflow furnace and is subjected to a certain reflow process to perform soldering.
Solder bridges may be formed during this type of soldering, and such solder bridges cause shorts between multiple lands. Therefore, after the solder printing process, the printed circuit board is inspected (see, e.g., Japanese Unexamined Laid-open Patent No. 2005-223281) to determine whether or not printing on the various lands has been properly performed. Then, if a solder bridge has been detected, a maintenance operation is performed, e.g., stoppage of the solder printer, cleaning or maintenance of the solder printer, or the like (see, e.g., Japanese Unexamined Laid-open Patent No. 2002-361830).
However, the presence or absence of such a solder bridge has been previously detected by inspecting only parts of the circuit board where the distance between lands is relatively short and where the occurrence of solder bridging is relatively easy. Among the solder bridges detected by this type of inspection, many solder bridges occur accidentally and as isolated events that are unrelated to whether operating conditions of the solder printing apparatus are good or bad. For this reason, there is concern that, if the solder printing apparatus is stopped every time such a minor solder bridge is detected and, performing the inspection operation would result in frequent stoppages of the manufacturing line and a marked worsening of productivity.
In order to prevent this worsening of productivity, a configuration has been considered, for example, that remembers the count of detected solder bridges and stops the solder printing apparatus only if the detected count exceeds a certain value. If some sort of major problem occurs, such as contamination of the metal mask, the frequency of occurrence of solder bridging greatly increases. Further, solder printing is continued under such conditions without performing maintenance on the solder printing apparatus, numerous printed boards with printing defects would be manufactured until the detected solder bridge count reaches a certain value, and yield dramatically declines.